Handle means for percussive tool



p 1956 w. D. KAISER ETAL HANDLE MEANS FOR PERCUSSIVE TOOL Filed Nov. 5, 1965 INVENTORS. W. KAI-55R J. C- SWAIN G. E. MANNING A'HORNEYs United States Patent 3,275,089 HANDLE MEANS FOR PERCUSSIVE TOOL Willard D. Kaiser, Grove City, and James C. Swain and George E. Manning, Columbus, Ohio, assignors, by mesne assignments, to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed Nov. 5, 1963, Ser. No. 321,610 7 Claims. (Cl. 173-162) This invention relates to percussive tools, and more particularly to the suspension means for the handles of such tools whereby the vibratory action at such handles is substantially reduced.

It is an accepted fact that prior art percussive tools such as pneumatic and hydraulic hammers, pavement breakers, and the like impart excessive vibratory action through their handles to the operator thereof; and numerous percussive handle structures have been devised in an attempt to reduce this vibratory action.

For example, pneumatic cushioning was disclosed in US. Patent No. 2,061,806, while US. Patents \No. 1,221,615 and No. 1,924,234 suggest utilization of cylinderand piston means interposed between the power mean-s and the handle. A variety of spring arrangements have been disclosed in US. Patents-No. 2,875,731 and No. 2,899,934, and in US. Patent No. 1,667,271, the handle for a percussive drill is located over the coincident with the axial plane of the tool body.

However, none of the prior art structures in the patents set out above satisfactorily solved the problem of eliminating vibration at the handle of a percussive tool.

The present invention contemplates the provision of an improved handle for a vibratory body which produces a percussive action by a fluid motor means. The handle is conveniently supported coincident with the axial plane of the vibratory body by a counterweighted support which is pivoted at a location offset from the axial center of the vibratory body. Basically, the solution to the problem of handle vibration in the present invention is solved by isolating a portion of the tool weight by utilization of a torsion means located at the handle frame pivot, frame geometry, and the proper selection of counterweight mass, springs, and location of handholds to result in the proper ratio of natural frequency of the system to the exciting frequency imposed.

In the preferred embodiment of the invention, a resilient torsion spring in the form of a rubber bushing is clamped at the pivotal mounting of the handle frame offset from the axial center of the vibratory body with a counterweight being provided at the free end of the handle frame. A lightweight metal such as aluminum for the handle frame allows a greater portion of handle weight to be localized at the counterweight mass, which, in the preferred embodiment, is made of steel to give rigidity to the handle frame. Further, a throttle for controlling the vibratory body pivots with the handle frame and yet remains in contact with a fluid pressure control valve for effective control of the percussive tool while being handled by an operator.

It is therefore an object of this invention to provide a center-of-rotation handle structure wherein a torsion means coacting therewith together with a counterweight substantially reduces vibration at the handle grips of a percussive tool.

It is another object of this invention to provide a torsionally isolated and counterweighted handle assembly for a percussive tool for minimizing vibration at said handle.

It is a further object of this invention to provide an improved handle assembly for a fluid-operated percussive tool for effectively reducing handle vibration by torsionally isolating said handle assembly.

3,275,089 Patented Sept. 27, 1966 ice These and other more specific objects and advantages of the invention will be apparent from the following detailed description.

A clear conception of the several improved features constituting the present invention, and of a commercial percussive tool operating in accordance therewith, may be had by referring to the drawings accompanying and forming a part of this specification, wherein like reference characters designate the same or similar parts in the various views:

FIGURE 1 is an elevation in perspective of a percussive tool such as a pavement breaker embodying the invention;

FIGURE 2 is an enlarged elevation of the handle assembly of the percussive tool of FIGURE 1;

FIGURE 3 is a plan view inpartial section of the handle assembly of FIGURE 2, wherein the figure is rotated 90 for clearness; and

FIGURE 4 is a schematic of an isolated mass relative to the tool body.

The tool structure illustrated in FIGURE 1 is a fluidpressure actuated percussive pavement breaker and embodies a conventional vibratory tool comprising a casing '20 having a fluid pressure motor (not shown) therein for percnssively actuating a pavement breaking member 2 1. To the upper end of casing 20 is mounted a tool head 22 and a control valve housing 23, to which handle assembly 25 is attached as described hereinafter.

Referring also to 'F IGURES 2 and 3, the handle assembly 25 comprises a pair of handles '26 secured to handle. frame members 27 and 28. The handle frame members are interconnected by a counterweight 29 as by bolts 24, thus forming a rigid handle assembly that is torsionally attached by a resilient bushing member 30 at pin B l which extends through the upper portion of control valve housing 23.

The resilient bushing member 30 in the preferred embodiment is constructed with a resilient material such as rubber or' the like that is retained by the clamping action of bolts 38 at control valve housing :33. The bushing member 30 serves as a torsion spring for isolating the mass of the handle assembly 25 including the counterweight 29, and, as the tool structure vibrates under percussive action, the handle assembly, being thus isolated by the resilient bushing member 30, will vibrate 180 out of phase with the tool. The operators bands will not feel the vibratory action at the handholds, as the handholds are located at the center of rotation of the handle assembly.

The center of rotation location for the handholds, as best viewed in FIGURE 4, is obtained by choosing the mass H of the handle assembly 25 in conjunction with a counterweight 29 to sum to a predetermined weight. By proper selection of handle assembly weight, counterweight, and tool body weight, it is possible to phase the vibration of the counterweight and the tool body mass B to be 180 apart. This causes the isolated mass H to be directed downwardly when the body mass B is directed upwardly, and vice versa. As a result, as seen in FIGURE 4, a point P on a lever L connecting mass H and mass B would sense only rotation and not vibration. Thus, the handhold is located at P, the center of rotation where only rotation and not vibration will be detected by the operator.

In the preferred embodiment, aluminum is used for the handle members 27, 28 to allow the greatest portion of the handle assembly weight to be located at the counterweight 29, thus allowing the center of rotation P to be more readily calculated as, for example, in the following V where w =natural frequency of the system in radians seconds K=isolatiug member, pounds/ inch g='acceleration of gravity, inches/seconds 'W =weight of tool body, pounds 'W =weight of handle, pounds In terms of the spring rate, handle mass, and the ex- 7 citing frequency, the equation to be used in the selection of thehandhold location is l where L =length from pivot to handholds, inches L =length from pivot to center of mass of the handle,

inches W=the exciting frequency of vibration, radians/second K=spring constant of separating spring between handle and body, pounds/inch v M =effective mass of'the handle, pound-second l inch Accordingly, as a specific example wherein Cycle rate: 1200 strokes per minute Weight of handle: 12 pounds Spring constant (K) 100 pounds] inch Then =401r radians/second E 12 v i 2 M 386 .0311 pound second Iinch.

Substituting in the equation to calculate the ratio used to determine handhold location To obtain a significant reduction in handle amplitude, a ratio of exciting frequency to the natural frequency'of the isolated mass H" must be at least two. It should be noted that an advantageof a hydraulic tool is that it allows a significant amount of weight to be saved in the basic tool body and incorporated in the counterweight mass thus more easily achieving the required ratio in accordancewith the above formula.

Pivotally attached at a pin 34 in handle 26 is a throttle 35 having an integral arm 36 for engaging plunger 37 of a control valve (not shown) in control valve housing 23. The arm 36 remains in contact with plunger 37 (see FIGURE 3) during operation of the tool structure for continuous control thereof.

actuated rock-drills, pavement breakers or the like,

Since the present invention is not concerned with the,

operation of the tool 20 as such but is only concerned with the shock-absorbing handle together with its suspension and counterweight, the operation of the tool has not been described herein in detail. However, reference is In summary, the invention consists of a fluid-pressure actuated percussive tool provided with a handle frame which is resiliently secured tothe vibratory tool body ata position laterally'otfset from the central axis of the tool to thereby isolate the handle frame from the percussive action of the tool body, the handle frame being formed with gripping means located at the center of rotation of the handle assembly. For ease of handling, the position was selected to coincide with the central axis of the tool. This, however, is not necessary for proper functioning. -In addition, the handle frame is provided with a counterweightzlocated adjacent to the gripping means and spaced from the resilient means securing the handle frame to the toolbody. p I l Theinvention has actually been incorporated ina hy draulically actuated pavement breaker, and tests have proven that a minimum of vibratory action-is transmitted to the operator. The improved device accordingly reduces the strain and fatigue towhieh the operator isnormally subjected, and the tool is also operated with greater effectiveness.

Thus, an improved handle assembly for a percussive. tool such as a pavement breaker has been described which substantially eliminates vibration'at the handle thereof by attaching. said handle frame'members to a housing offset from the central axis of the percussivetool by means ,of a resilient bushing for isolating the mass of the handle assembly including a counterweight secured to-said handle members, and wherein the handles are located at the center of rotation and transverse thereto on the handle frame members between said counterweight and said resilient bushings. I p

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention: 7

- We claim: Y.

1. In a fluid pressure actuated percussive tool having a vibratory tool body, a handle frame, means resiliently securing said handle frame to said vibratory tool body laterally offset from the central axis of said tool to isolate I said handle frame from the percussive action of said vibratory tool body, gripping, means on said handle frame 'lo-:

cated in a plane substantially coinciding with the central axis of the tool, and a counterweight on said handle frame 7 securing means is a resilient bushing having a longitudinal axis substantially parallel to the longitudinal axis of;said' gripping handles to permit limited swinging movement of the handle frame. 7 V

5. The combination of claim 4, whereinthrottle means 7 is pivotally carried by said handle" frame for continuously made to such patents as US. Patents No. 2,061,806,No.

2,531,800, and No. 3,028,840 which all illustrate and describe percussion tools of the general type towhich .the present invention would be applicable.

engaging a control element carried on said tool.

6. In a vibration-isolated handle assembly for a percussive tool having a vibratory body, the combination of: mounting means on said tool body for torsionally attach ing said handle assembly a spaced distance laterally oifset from the central axis of said tool body, aresilient bushing interposed between said. mounting means=and said handle assembly for'providing visolation between said mounting and said assembly; said handle assembly through and transverse to the center of rotation of the handle assembly whereby percussive action of said tool is thus isolated from said handle assembly by said resilient bushing to render the handle means substantially vibration-free.

7. The combination of claim 6, wherein said handle assembly including said counterweight and handle means constitutes a first mass, said tool body and mounting means constituting a second mass, and said resilient bushing interposed between said first and second masses substantially resulting in said first mass vibrating out of phase at a predictable amplitude ratio from said second mass to allow location of handholds on said handle assembly at the center of rotation which is substantially vibration free. 7

6. References Cited by the Examiner UNITED STATES PATENTS 2/1953 Anderson 173-162 3/1953 Wallerstein 173162 FOREIGN PATENTS 565,783 11/1944 Great Britain.

0 FRED C. MATTERN, 111., Primary Examiner.

BROUGHTON G. DURHAM, Examiner.

L. P. KESSLER, Assistant Examiner. 

1. IN A FLUID PRESSURE ACTUATED PERCUSSIVE TOOL HAVING A VIBRATORY TOOL BODY, A HANDLE FRAME, MEANS RESILIENTLY SECURING SAID HANDLE FRAME TO SAID VIBRATORY TOOL BODY LATERALLY OFFSET FROM THE CENTRAL AXIS OF SAID TOOL TO ISOLATE SAID HANDLE FRAME FROM THE PERCUSSIVE ACTION OF SAID VIBRATORY TOOL BODY, GRIPPING MEANS ON EACH HANDLE FRAME LOCATED IN A PLANE SUBSTANTIALLY COINCIDING WITH THE CENTRAL AXIS OF THE TOOL, AND A COUNTERWEIGHT ON SAID HANDLE FRAME LOCATED ADJACENT TO SAID GRIPPING MEANS REMOTE FROM SAID RESILIENT SECURING MEANS. 